1. Field of the Invention
This invention relates to a color tunable light source and in particular to a light source based on a light emitting diode (LED) arrangement. Moreover the invention provides a method of generating light of a selected color.
2. Description of the Related Art
Currently, the color of light generated by a light source, in particular light emitting diodes (LEDs), is determined by the physical mechanism used to generate the light. For example, many LEDs incorporate one or more phosphor materials, that is photo luminescent materials, which absorb a portion of the radiation emitted by the LED chip/die and re-emit radiation of a different color (wavelength). The color of light generated by such LEDs is the combined light from the LED chip and Phosphor which is fixed and determined when the LED is fabricated.
It is also known to use a color filter with incandescent, fluorescent and other light sources to generate a selected color of light. To change the color of light requires replacement of the filter.
Color switchable light sources are known which comprise red, green and blue LEDs. The color of light output from such a source can be controlled by selective activation of one or more of the different colored LEDs. For example activation of the blue and red LEDs will generate light which appears purple in color and activation of all three LEDs produces light which appears white in color. A disadvantage of such light sources is the complexity of driver circuitry required to operate these sources.
U.S. Pat. No. 7,014,336 discloses systems and methods of generating colored light. One lighting fixture comprises an array of component illumination sources, different color LEDs, and a processor for controlling the collection of component illumination sources. The processor controls the intensity of the different color LEDs in the array to produce illumination of a selected color within a range bounded by the spectra of the individual LEDs and any filters or other spectrum-altering devices associated with the lighting fixture.
The present invention arose in an endeavor to provide a colored light source whose color is at least in part tunable.